This specification relates to image processing.
The Internet provides access to a wide variety of resources such as video or audio files, web pages for particular subjects, book articles, or news articles. There are many resources available, and to help users find resources that may be of interest to them, many companies have developed search systems that identify resources in response to a query. For textual searches, search queries usually are terms and phrases. For image searches, such as search of still images and videos, the search queries can be images, or terms and phrases, or a combination of images, terms and phrases. A search system ranks the resources in response to the query and provides search results that link to the identified resources. The search results are typically ordered for viewing according to the rank.
When searching images, a search system may use a trained model function to identify images that are similar to a search query image. A variety of model functions can be used. Many of these trained models are optimized to identify images that belong to a same category.